The present invention relates to a construction material for vehicles consisting of a formable sandwich material. More particularly, the present invention relates to such construction material of the type with at least two plates, at least one of which has been covered with fiber flocks by electrostatic deposition on that surface facing the second plate. Accordingly, the material consists of two plates with intermediate fibers which are generally perpendicular to the plates, and which have been fastened to the plates by means of a binder on each plate.
A considerable number of different types of sandwich materials are known. They typically consist of two sheets or plates between which are arranged material of a softer type. The sheets or plates may be comprised of the same or different material, and the material between them may be homogeneous or composite. The sandwich materials are often rigid and strong compared to their weight and are used, inter alia, as building materials, packing materials and the like.
A specific type of sandwich material is described in European Patent No. 333,685. In this material plates of steel, aluminum or the like which are electrically conductive are used as the outer material, whereas the material between them consists of fibers which have been arranged by electrostatic deposition, known as flocking. Before the flocking is carried out, the fibers are cut into suitable lengths having a size in the order of 1 mm, and are introduced into an electrical field thereby becoming electrically charged and attracted by a plate which is preferably grounded. On this grounded plate a binder has been applied, and when the fibers, through the electrostatic field, are rapidly attracted to the plate, they land thereon in an to the plate they land thereon in an upright position and are fastened in the binder. The binder is finally cured and the velvet-like surface which consists of fibres is cleaned of fibres which have not fastened. According to this patent, two plates may be covered with fibre flock and pressed against each other so that the fibres penetrate in between each other. To attach the plates to each other strips or patches of glue may be applied on some of the flocked surfaces. However, according to the patent only one plate may be flocked, with the result that it will be necessary to apply a film of binder on the other plate to hold the sandwich material together.
This sandwich material is made up of electrically conductive plates such as aluminium, steel or the like or some other electrically non-conductive material such as plastic sheets. However, the intermediate flock consists of electrically non-conductive material such as nylon fibres.
This laminate or sandwich material can be formed in different ways without breaking. The material is very light compared to its thickness and has a great mechanical strength.
Technical Problem
The above-mentioned and other known sandwich materials have many advantages but they nevertheless have the disadvantage that a substantial part of the composition consists of organic materials, which means that the material is not suitable for high temperatures especially during longer periods. Nylon fibres or other suitable polymer fibres melt at around 100xc2x0 C. and therefore this material must be used at substantially lower temperatures in order to maintain its properties. This limits the application area of this material. For example, it cannot be used for such details on cars which have to be painted since the painting occurs at temperatures of 200-300xc2x0 C. A further problem with the known materials is that they are not environmental friendly since they are composed of different materials.
Solution
It has therefore long been a desire to bring about a sandwich construction material as a construction material in vehicles which is light, is formable, has suitable mechanical properties such as rigidity and elasticity and which above all can resist high temperatures. According to the present invention, there has therefore been brought about a formable sandwich material comprising at least two plates at least one of which is covered by fibres on that side which faces the second plate or alternatively on both sides by means of electrostatic deposition, known as flocking, and which includes the fibres substantially consisting of metallic material.
According to the invention, it is suitable that the fibres consist of stainless steel, aluminium or some other metal or alloys.
The plates in the sandwich material can, according to the invention, be made of the same material as the fibres or of some other metallic material.
According to the invention, it is suitable that the material both in the plates and the fibres consists of stainless steel and that the thickness of the plates lies between 0.4-0.05 mm and the length of the fibres between 1-3 mm and their thickness between 8-30 micrometers.
The thickness of the aluminium fibres may be between 30-50 micrometers.
According to the invention, both the plates may be covered with fibres on that side which faces the other plate.
According to the invention, it is also possible that only one plate is covered with fibres whereas the other plate is provided with a thin layer of an adhesive.
According to the invention, the sandwich material may comprise more than two plates with intermediate flocks.
The sandwich material according to the present invention is suitable for use as a construction material in vehicles, preferably as a bonnet, boot lid, roof (hard top), sound-absorbing plates, etc.
If the material according to the present invention is used as a roof on a car, it may suitably be flocked also on that surface of the laminate which faces inwardly into the vehicle.
If, as according to the above, the material is used as a roof on a vehicle, such as for example, a private car and the material comprises stainless steel, that side of the roof which faces outwardly can be free from paint and instead be polished or embossed in a suitable pattern.